Investigations of human exposure to environmental contaminants were funded by this research budget in FY2017 as follows: 1) Anniston community health survey (ACHS-II): Follow-up study and dioxin analyses. This is a major cross-sectional epidemiology investigation in residents of Anniston, Alabama exposed over time to PCBs and other contaminants from a local chemical production facility. A previous study conducted by the Agency for Toxic Substances and Disease Registry (ATSDR) of the CDC found elevated blood levels of PCBs in the population associated with a high incidence of hypertension and diabetes. The current study partners with ATSDR to assess current blood concentrations of non-dioxin-like and dioxin-like PCBs, other dioxin-like chemicals, persistent pesticides, and heavy metals in some participants of the earlier study. The results will be used for health and risk management for the exposed individuals. The recruitment and sampling phases of this study are concluded. Blood was collected from 359 of 777 subjects from the original study. Laboratory analysis of these samples is underway. Preliminary results from some participants indicate a decrease over time in serum levels of many PCB congeners, especially those of lowest chlorination. New research is underway to assess the degree of DNA methylation (biomarker of chemical exposure) in these subjects. 2) Toxic organic chemicals and heavy metals in blood and urine of electronic waste recycling workers and the general population in rural Vietnam. This collaborative study with Vietnamese researchers and others compares concentrations of heavy metals, PCBs, dioxins, and other POPs in e-waste recyclers and a control cohort. Sample analysis conducted in FY2015 detected elevated levels of some organic pollutants in the workers and of some heavy metals in subjects from both cohorts. Results from these studies were reported at scientific meetings in FY2017 and a manuscript describing the Biomonitoring of Organics and Metals in Vietnamese Female Electronic Waste Recyclers has been accepted for publication. 3) Bisphenol A (BPA) pharmacokinetics: Controlled exposure study. This study is being conducted in collaboration with NIEHS and NTP researchers. The results for an oral exposure to 14 subjects were published in FY2015. Dermal application studies are in progress. These data will be used for further understanding of the fate of this potential endocrine disruptor in humans. Studies of the fate and toxicity of several brominated flame retardants (BFRs) were conducted in the PI's research laboratory in FY2017 as follows: 1) Studies of the major flame retardant tetrabromobisphenol A (TBBPA) Wistar Han rats chronically exposed to TBBPA by the oral route have a higher incidence of uterine tumors than in controls. Studies were designed to characterize this mechanism of toxicity. A study of the fate of TBBPA in female rats did not detect evidence for accumulation of TBBPA or generation of TBBPA-derived reactive metabolites in uterine tissues. Therefore, the most likely hypothesis for the carcinogenic response involved disruption of estrogen and/or thyroid hormone homeostasis in the TBBPA-exposed rats. This hypothesis was subsequently supported by the results of molecular studies conducted in the laboratory. A manuscript of these results was published in FY2017. Humans are at risk for dermal exposure to TBBPA; therefore, a study was conducted with USEPA researchers for predicting bioavailability of TBBPA in humans. This was accomplished by comparing results of TBBPA dermal exposure in intact rats with that of in vitro exposure to rat and human skin. These studies are completed and data were published in FY2017. Humans may also be at risk for developmental exposure to low-doses of TBBPA in the environment. Data are needed in a rodent model for extrapolation purposes; therefore, a collaborative study of prenatal and perinatal exposure to TBBPA in rats is being conducted with other NIEHS researchers. Results from the collaborative prenatal & perinatal were reported at scientific meetings in FY2017 and a manuscript describing the disposition of TBBPA in pregnant and nursing rats has been submitted for publication. 2) Studies of novel and emerging BFRs Some legacy BFRs, e.g. polybrominated diphenyl ethers (PBDEs), have accumulated in the environment, wildlife, and humans. These BFRs are being replaced with newer brominated chemicals such as 1-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), bis(2-ethylhexyl) tetrabromophthalate (BEH-TEBP), and decabromodiphenyl ethane (DBDPE). However, adequate toxicological evaluations for these chemicals are lacking. Toxicokinetic studies are being conducted in this laboratory to provide supporting data for designing and interpreting toxicity studies and risk assessments for these chemicals. These studies presently include investigations of the fate of each chemical in rodents by different exposure routes, with emphasis on determining bioavailability, detoxication and activation pathways, target tissues and accumulation potential, and rates and routes of dose excretion. Results of these studies were reported at scientific meetings in FY2016 and journal articles describing completed studies were published in FY2017. Additional studies are being designed as needed. 3) Studies of the major flame retardant 2,4,6-tribromophenol (TBP) TBP has been long used as a flame retardant and wood fungicide and is both a precursor for, and degradation product of, PBDEs. TBP exposure in human populations is ubiquitous. TBP has recently been shown to accumulate in placenta by unknown mechanisms. However, adequate toxicological evaluations for TBP is lacking and toxicokinetic studies are being conducted in this laboratory to provide supporting data for designing and interpreting toxicity studies and risk assessments for TBP. These studies presently include investigations of the fate of TBP in rodents by different exposure routes, with emphasis on determining bioavailability, detoxication and activation pathways, target tissues and accumulation potential, and rates and routes of dose excretion. Results of these studies will be reported at scientific meetings in FY2018. 4) Studies of efflux transporter activity and function in barrier tissues following xenobiotic exposure The blood-brain barrier and the placental barrier protect the brain and the developing fetus. Both are composed of vasculature that contain tight junctions and ABC transporters that hinder the entry of xenobiotics to the brain and the placenta. Earlier studies indicate that signal transduction pathways regulate the activity and expression of numerous transporters that line the lumen of the microvessels in the brain and the placenta. Our overall research objective is to determine if xenobiotics cross these barriers and/or modulate the ABC transporters. Current studies are focused on the effects of the brominated flame retardants TBBPA and TBP on transporter function and expression. Ex vivo experiments in rats have been performed to measure both expression and transport activity following exposure to TBBPA and TBP. Known agonists and antagonists have been used to tentatively identify the signaling pathways involved in the regulation of two canonical transporters, P-glycoprotein (Pgp, ABCB1) and breast cancer resistance protein (BCRP, ABCG2) following exposure in culture. Westerns and IHC have been performed to quantitate steady state protein levels. Additional studies are being designed to validate ex vivo findings using an in vivo model designed to measure the entry of radiolabeled substrates in brain and placenta. Results of these studies will be reported at scientific meetings in FY2018.